McClatchy Newspapers: Scientist Anne Hershey paddled a small inflatable raft across an arctic lake, pausing in her stroke to consider how the melting permafrost caused a landslide of mud and sediment spilling down the bank into the water. Since the bank collapsed two years ago, the water has grown cloudy with sediment, providing scientists a natural laboratory for studying how warmer temperatures may play out in ecosystems far and near. Global air and water temperatures are inching up, causing seas …